Re: [PATCH Resend] cpufreq: Set cpufreq_cpu_data to NULL before putting kobject

[ethan zhao]

On 2015/2/2 11:43, Viresh Kumar wrote:
> On 2 February 2015 at 09:08, ethan zhao <ethan.zhao@xxxxxxxxxx> wrote:
> > > We take cpufreq_driver_lock() here, and so this will
> > > block thread B.
> >   No, there is no  cpufreq_driver_lock acquired between
> >
> >   cpufreq_cpu_get()  and cpufreq_cpu_put()
> I am not saying that the lock is taken between them. But within
> cpufreq_cpu_get() to make sure policy doesn't get freed while we
> are doing kobject_get().
 How to prevent the policy to be freed between

cpufreq_cpu_get()  and cpufreq_cpu_put() ?

> > > >              beginning the deference of policy        Thread B:
> > > >              ... ... __cpufreq_remove_dev_finish()
> > > > cpufreq_policy_free(policy);
> > > >
> > > >
> > > > Perhaps move policy->rwsem out side the policy structure is a way to
> > > > avoid
> > > > it completely.
> > > > and you could stopping the PPC thread stepping forward as my patch as
> > > > temporary workaround.
> > > I couldn't understand your problem completely. Apart from giving a
> > > detailed
> > > look of what's going on both threads, always specify where the BUG
> > > actually
> > > is..
> > The problem is you are using a rwsem inside policy structure to protect its
> > assessment, that is bad design.
> What is the current bug you are facing right now, I haven't understood it well.
> Also a lock within the structure isn't new. Its all over the kernel. I
> don't understand
> why you say its a bad design.
You are maxing up the water with sand ?

Thanks,
Ethan

> --
> viresh

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